Achalasia is a premalignant condition and a risk factor for the development of esophageal squamous cell carcinoma. Achalasia may also increase the risk for esophageal adenocarcinoma. However, achalasia is associated with decreased risk of gastroesophageal reflux disease because the hypertensive lower esophageal sphincter retards acid reflux into the esophagus. GISTs and gastric adenocarcinoma are not associated with achalasia.